1. Field of Invention
The present invention relates to a humidity sensing structure and a method therefor. More particularly, the present invention relates to a structure for sensing the humidity of the environment by using a resistive-type microbridge structure and a fabricating method.
2. Related Art
Recently, the common sensing principles of the humidity sensor include interdigitated electrode (IDE) type, piezoresistive type, surface acoustic wave (SAW) type and optical type etc. The various sensors have their own advantages; however, disadvantages such as low sensitivity, low stability, weak linearity, long responding time and incompensatable excursion value due to the variation of the temperature still exist. In order to solve the bottleneck or the shortcoming of the above technologies and to satisfy the design trend for the sensing module of being miniaturized, portable, and having integrated system, recently the so-called integrated humidity sensing is developed.
In Taiwan patent publication No. 200,508,590 entitled “Micro sensor and Fabricating Method therefor and Sensing Apparatus Using the Same”, the capacitance value of a capacitor changes as a cantilever beam bents, so as to change the distance between a fixed electrode layer and a movable electrode layer. Although it is proved that the cantilever beam structure of the microelectromechanical process has the features of higher sensing sensitivity and shorter responding time, because of the process for the top cover element of the fixed electrode in the structure and the subsequent packaging process, the process yield and the packaging cost of the sensing element have the space to be modified. In addition, in the process of the cantilever beam structure of the microelectromechanical process, because only one end is fixed, in the subsequent chip packaging process, the sensing chip of the cantilever beam has an unstable yield. Therefore, the application to the low cost sensor has the room for improvement.